1/3 of the people living in Estonia do not speak fluent estonian (or do not speak the language at all).
Those are the descendants of the former occupation forces, Russians who are encouraged by their nations leaders to stay on the formerly occupied territories and to resist integration.
Strangely enough the EU and the world community fail to approve of Estonia-s attempt to assimilate the next generation by making estonian the mandatory teaching language at schools, i.e. to acquire adequate skills inte local tongue. (For clarity I must add that Estonia in no way tries to prevent studying or using russian; the objective is to make the russian descendants adopt estonian in addition to their own language.)